Radio paging systems are well known and widely used. Upon receipt of a page, conventional radio paging systems provide a user with audio and/or visual information from the paging party, but cannot transmit information back to the paging party. Recently, national and international paging services have been implemented so that individuals may receive a page throughout the United States or throughout Europe. Despite the advances in paging technology, a significant disadvantage of radio paging is that after an individual carrying a pager has learned that a paging party wishes to communicate, that individual must locate a telephone communication system to contact the paging party and pay for this contact.
Radio paging systems typically include a radio transmitter for transmitting a coded radio frequency signal associated with a party to be paged and a portable paging receiver. To contact a party carrying a pager, a person dials a telephone number. The number is transferred by the public switched telephone network (PSTN) to the radio transmitter. The transmitter transmits a page signal coded to all pagers in the range of the transmitter. Because each mobile pager responds to a different paging code, only the pager having a code corresponding to that transmitted is activated. The activated pager generates an audible tone or some other signal to notify the designated party that he or she has been paged. That party typically responds by calling a specific telephone number to receive further instructions.
One advantage of paging systems is that they can serve relatively large geographic areas. Another advantage is that a paging subscriber may be reached anywhere in the transmitter coverage area without the paging system knowing the location of that subscriber. As described above, the major disadvantage of paging systems is that a subscriber cannot immediately communicate with the person who initiated the call. In fact, in conventional paging systems, the subscriber cannot even acknowledge that he or she has received the page. Also, calling back later entails cost.
In contrast, mobile radio telephone systems allow flexible two way radio communications with a plurality of mobile subscribers. Cellular telephones allow subscribers to be paged immediately over cellular radio paging frequencies (as long as the phone unit is on). The mobile telephone responds immediately to a page and gets a voice channel assigned for the communication. In addition, cellular subscribers may of course initiate calls themselves. Unfortunately, mobile telephones cannot be paged while the mobile telephone is turned off or deactivated. Also, mobile telephones are heavier than pagers and a cellular page may not be heard by the subscriber if he/she has left the mobile telephone in an on-state in the vicinity but out of hearing distance.
One disadvantage with cellular telephoning is that a subscriber's location must be known to the cellular system. Subscriber location is known by registering each mobile, e.g. periodically. In contrast, conventional paging systems do not require individual pagers to register. Thus, paging services are advantageous in situations where a subscriber desires to keep his exact location secret but still wants to have the option of being contacted.
Recently, it has become possible to subscribe to a cellular service and to an independent paging system. Telephone calls from the land based telephone network are attempted initially with the mobile station over the cellular network. If the subscriber does not answer, the call is diverted to an FM radio paging system. A cellular pager is disclosed in U.S. Statutory Invention Registration H 610 to Focarile et al. In this system, a separate paging system is used in conjunction with the cellular telephone system. The paging system provides a backup for cellular telephone calls intended for an associated cellular telephone which has been deactivated because the subscriber is, for example, temporarily away from his automobile. Since the pager is assigned the same number as the telephone, the pager provides an alert signal to the subscriber of the cellular telephone indicating that a call has been attempted to the subscriber's telephone. Later, the subscriber may call an appropriate service number at his/her own expense for the information about the earlier call when the subscriber returns to the automobile and activates the cellular telephone.
UK Patent No. 2 230 162 to Rodriguez physically combines a pager and a hand held cellular mobile radio terminal whereby the pager is connected to the hand held cellular mobile radio terminal in order to be able to keep the hand held terminal in a switched off mode to save battery power, but still be accessible for incoming calls. When a call is being directed toward the handheld terminal, the pager is first paged which then automatically switches on the handheld terminal so that the handheld terminal can receive the call which is redirected to the mobile terminal. However, the method taught by Rodriguez needs a specially modified handheld terminal and pager. It would be desirable to use standard handheld terminals and pagers to achieve the same battery savings as in Rodriguez although battery savings is not such an important problem anymore due to recent technical progress in this field. Furthermore, it is desirable to give a subscriber carrying a pager in the on-state and a cellular telephone in the off-state a chance to screen incoming calls and to decide whether to answer a call rather than having the pager automatically switching the cellular telephone on. Furthermore, it is desirable for a subscriber receiving a call to have a pager and a handheld terminal which are physically separate in order to allow the user to carry only the pager while having the heavier handheld somewhere in the vicinity and still enable answering of a call.